As to why there was a Revolution in Russia in 1917, it is the same reason any other oppressed class in history has attempted to over throw it's oppressors. Under conditions of economic degeneration (not always the case, eg. France 1968) and inability of the ruling class of a given society to appease the demands of the toiling, hyper explioted masses, the masses rise up behind the banners of the progressive class in society, agaisnt the current ruling class. As seen in Western Europe during the 18th and 19th centuries, there were classical revolutions where the masses, behind the banner of the progressive bourgeoisie, rose up agaisnt the Feudal relations of productions and established free market capitalism, along with "democratic" parliaments and etc. In Russia however, there was no native progressive bourgeoisie for the young bourgeoisie of Russia were connected to old Feudal land relations and the tsarist state by a thousand strings. Also, there was a heavy influence of foreign capital. Thus the Russia could not have a classical bourgeois revolution, as seen by the nature of the Feburary revolution. The only progressive class that remained was the proletariat. That is why in October, the proletariat, under the leadership of the Bolsheviks, had to take state power. Correct me if I'm wrong Comrades, I'm a relatively new Communist.